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Photonic crystal structures with tunable structure color as colorimetric sensors.

Wang H, Zhang KQ - Sensors (Basel) (2013)

Bottom Line: In particular, some kinds of the structural colors in living organisms can be reversibly changed in reaction to external stimuli.Based on the lessons learned from natural photonic structures, some specific examples of PCs-based colorimetric sensors are presented in detail to demonstrate their unprecedented potential in practical applications, such as the detections of temperature, pH, ionic species, solvents, vapor, humidity, pressure and biomolecules.The combination of the nanofabrication technique, useful design methodologies inspired by biological systems and colorimetric sensing will lead to substantial developments in low-cost, miniaturized and widely deployable optical sensors.

View Article: PubMed Central - PubMed

Affiliation: National Engineering Laboratory for Modern Silk, College of Textile and Clothing Engineering, Soochow University, Suzhou 215123, China. whui@suda.edu.cn

ABSTRACT
Colorimetric sensing, which transduces environmental changes into visible color changes, provides a simple yet powerful detection mechanism that is well-suited to the development of low-cost and low-power sensors. A new approach in colorimetric sensing exploits the structural color of photonic crystals (PCs) to create environmentally-influenced color-changeable materials. PCs are composed of periodic dielectrics or metallo-dielectric nanostructures that affect the propagation of electromagnetic waves (EM) by defining the allowed and forbidden photonic bands. Simultaneously, an amazing variety of naturally occurring biological systems exhibit iridescent color due to the presence of PC structures throughout multi-dimensional space. In particular, some kinds of the structural colors in living organisms can be reversibly changed in reaction to external stimuli. Based on the lessons learned from natural photonic structures, some specific examples of PCs-based colorimetric sensors are presented in detail to demonstrate their unprecedented potential in practical applications, such as the detections of temperature, pH, ionic species, solvents, vapor, humidity, pressure and biomolecules. The combination of the nanofabrication technique, useful design methodologies inspired by biological systems and colorimetric sensing will lead to substantial developments in low-cost, miniaturized and widely deployable optical sensors.

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(A) Top view and cross-sectional view of the SEM images of as-prepared 1D TiO2 PCs films. The high and low-density regions of the structure are labeled. All the scale bars indicate 200 nm. (B) Colorful photographs of the sensor taken under the low and high humidity environments. (C) Sensitivity of device. Sensitivity values above the dashed red line indicate that a 1% RH change causes a detectable color change in the PC sensor [34].
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f7-sensors-13-04192: (A) Top view and cross-sectional view of the SEM images of as-prepared 1D TiO2 PCs films. The high and low-density regions of the structure are labeled. All the scale bars indicate 200 nm. (B) Colorful photographs of the sensor taken under the low and high humidity environments. (C) Sensitivity of device. Sensitivity values above the dashed red line indicate that a 1% RH change causes a detectable color change in the PC sensor [34].

Mentions: PCs can be employed to sense not only solvents but also various chemical vapors. As the changes in the refractive index or the lattice spacing are determined by the filling ratio of the gaseous species, the vapor sensor actually measures the partial pressure of the vapor. A useful technical extension of such systems is the humidity sensor, which provides information of water vapor content in gaseous atmospheres [34–38]. For inorganic humidity sensors, structural color changes are often caused by changes in effective refractive index. Hawkeye et al. developed a mesoporous TiO2 PCs with high- and low-density structural layers constituting of high- and low-refractive index layers (Figure 7(A)) [34]. It is shown that the structural color changes of TiO2 PCs can be sensitively observed despite the fact that the relative humidity changes are smaller than 1%. The colorful response of the sensor lasts over hundreds of hours (Figure 7(B and C)). Hydrogel-based sensors generally induce a diffraction wavelength shift in response to humidity changes, owing to the volume change of polymer networks. Wang et al. developed a humidity sensor by infiltrating acrylamide (AAm) solution into a P(St–MMA–AA) photonic crystal template and subsequently photo-polymerizing [35]. The colors of such sensors could reversibly vary from transparent to violet, blue, cyan, green and red under various humidity conditions, covering the whole visible range. Furthermore, the color response showed exceptional stability under cyclic humidity experiments. Yang et al. reported an organic/inorganic hybrid 1D PCs consisting of alternating thin films of titania and poly(2-hydroxyethyl methacrylate-co-glycidyl methacrylate) (PHEMA-co-PGMA) by the simple, reproducible, and low-cost approach of spincoating [36]. Park et al. developed fast responsive polymeric humidity sensors from a series of self-assembled poly(styrenesulfonate-methylbutylene) (PStS-b-PMB) block copolymers with tailored hygroscopic properties [37]. Under different humidity, the PStS-b-PMB thin films displayed discernible reflective color changes covering almost entire visible light regions from violet (RH = 20%) to red (RH = 95%).


Photonic crystal structures with tunable structure color as colorimetric sensors.

Wang H, Zhang KQ - Sensors (Basel) (2013)

(A) Top view and cross-sectional view of the SEM images of as-prepared 1D TiO2 PCs films. The high and low-density regions of the structure are labeled. All the scale bars indicate 200 nm. (B) Colorful photographs of the sensor taken under the low and high humidity environments. (C) Sensitivity of device. Sensitivity values above the dashed red line indicate that a 1% RH change causes a detectable color change in the PC sensor [34].
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC3673079&req=5

f7-sensors-13-04192: (A) Top view and cross-sectional view of the SEM images of as-prepared 1D TiO2 PCs films. The high and low-density regions of the structure are labeled. All the scale bars indicate 200 nm. (B) Colorful photographs of the sensor taken under the low and high humidity environments. (C) Sensitivity of device. Sensitivity values above the dashed red line indicate that a 1% RH change causes a detectable color change in the PC sensor [34].
Mentions: PCs can be employed to sense not only solvents but also various chemical vapors. As the changes in the refractive index or the lattice spacing are determined by the filling ratio of the gaseous species, the vapor sensor actually measures the partial pressure of the vapor. A useful technical extension of such systems is the humidity sensor, which provides information of water vapor content in gaseous atmospheres [34–38]. For inorganic humidity sensors, structural color changes are often caused by changes in effective refractive index. Hawkeye et al. developed a mesoporous TiO2 PCs with high- and low-density structural layers constituting of high- and low-refractive index layers (Figure 7(A)) [34]. It is shown that the structural color changes of TiO2 PCs can be sensitively observed despite the fact that the relative humidity changes are smaller than 1%. The colorful response of the sensor lasts over hundreds of hours (Figure 7(B and C)). Hydrogel-based sensors generally induce a diffraction wavelength shift in response to humidity changes, owing to the volume change of polymer networks. Wang et al. developed a humidity sensor by infiltrating acrylamide (AAm) solution into a P(St–MMA–AA) photonic crystal template and subsequently photo-polymerizing [35]. The colors of such sensors could reversibly vary from transparent to violet, blue, cyan, green and red under various humidity conditions, covering the whole visible range. Furthermore, the color response showed exceptional stability under cyclic humidity experiments. Yang et al. reported an organic/inorganic hybrid 1D PCs consisting of alternating thin films of titania and poly(2-hydroxyethyl methacrylate-co-glycidyl methacrylate) (PHEMA-co-PGMA) by the simple, reproducible, and low-cost approach of spincoating [36]. Park et al. developed fast responsive polymeric humidity sensors from a series of self-assembled poly(styrenesulfonate-methylbutylene) (PStS-b-PMB) block copolymers with tailored hygroscopic properties [37]. Under different humidity, the PStS-b-PMB thin films displayed discernible reflective color changes covering almost entire visible light regions from violet (RH = 20%) to red (RH = 95%).

Bottom Line: In particular, some kinds of the structural colors in living organisms can be reversibly changed in reaction to external stimuli.Based on the lessons learned from natural photonic structures, some specific examples of PCs-based colorimetric sensors are presented in detail to demonstrate their unprecedented potential in practical applications, such as the detections of temperature, pH, ionic species, solvents, vapor, humidity, pressure and biomolecules.The combination of the nanofabrication technique, useful design methodologies inspired by biological systems and colorimetric sensing will lead to substantial developments in low-cost, miniaturized and widely deployable optical sensors.

View Article: PubMed Central - PubMed

Affiliation: National Engineering Laboratory for Modern Silk, College of Textile and Clothing Engineering, Soochow University, Suzhou 215123, China. whui@suda.edu.cn

ABSTRACT
Colorimetric sensing, which transduces environmental changes into visible color changes, provides a simple yet powerful detection mechanism that is well-suited to the development of low-cost and low-power sensors. A new approach in colorimetric sensing exploits the structural color of photonic crystals (PCs) to create environmentally-influenced color-changeable materials. PCs are composed of periodic dielectrics or metallo-dielectric nanostructures that affect the propagation of electromagnetic waves (EM) by defining the allowed and forbidden photonic bands. Simultaneously, an amazing variety of naturally occurring biological systems exhibit iridescent color due to the presence of PC structures throughout multi-dimensional space. In particular, some kinds of the structural colors in living organisms can be reversibly changed in reaction to external stimuli. Based on the lessons learned from natural photonic structures, some specific examples of PCs-based colorimetric sensors are presented in detail to demonstrate their unprecedented potential in practical applications, such as the detections of temperature, pH, ionic species, solvents, vapor, humidity, pressure and biomolecules. The combination of the nanofabrication technique, useful design methodologies inspired by biological systems and colorimetric sensing will lead to substantial developments in low-cost, miniaturized and widely deployable optical sensors.

Show MeSH